Process for arylamine production

ABSTRACT

Forming a 4-aminobiphenyl derivative arylamine compound, includes (i) providing a first disubstituted 4-aminobiphenyl compound; (ii) optionally formylating the first disubstituted 4-aminobiphenyl compound to form a bisformyl substituted compound where the first disubstituted 4-aminobiphenyl compound is not a bisformyl substituted compound; (iii) acidifying the bisformyl substituted compound to convert formyl functional groups into acid functional groups to form an acidified compound; and (iv) hydrogenating the acidified compound to saturate at least one unsaturated double bonds in the acidified compound.

BACKGROUND OF THE INVENTION

1. Field of Invention

This invention relates generally to improved chemical processes for thesynthesis of arylamine compounds, and to the use of such arylaminecompounds in producing overcoating layers for electrophotographicimaging members. In particular, this invention provides a process forforming a 4-aminobiphenyl derivative arylamine compound, such asN,N-[3-carboxypropyl phenyl]-4-aminobiphenyl or its alkali metal salt,using a direct hydrogenation reaction on a carboxylate salt.

2. Description of Related Art

In electrophotography, an electrophotographic substrate containing aphotoconductive insulating layer on a conductive layer is imaged byfirst uniformly electrostatically charging a surface of the substrate.The substrate is then exposed to a pattern of activating electromagneticradiation, such as, for example, light. The light or otherelectromagnetic radiation selectively dissipates the charge inilluminated areas of the photoconductive insulating layer while leavingbehind an electrostatic latent image in non-illuminated areas of thephotoconductive insulating layer. This electrostatic latent image isthen developed to form a visible image by depositing finely dividedelectroscopic marking particles on the surface of the photoconductiveinsulating layer. The resulting visible image is then transferred fromthe electrophotographic substrate to a necessary member, such as, forexample, an intermediate transfer member or a print substrate, such aspaper. This image developing process can be repeated as many times asnecessary with reusable photoconductive insulating layers.

In image forming apparatus such as copiers, printers and facsimiles,electrophotographic systems in which charging, exposure, development,transfer, etc. are carried out using electrophotographic photoreceptorshave been widely employed. In such image forming apparatus, demands forspeeding up of image formation processes, improvement in image quality,miniaturization and prolonged life of the apparatus, reduction inproduction cost and running cost, etc. are increasingly growing.Further, with recent advances in computers and communication technology,digital systems and color image output systems have been applied also tothe image forming apparatus.

Electrophotographic imaging members (i.e. photoreceptors) are wellknown. Electrophotographic imaging members are commonly used inelectrophotographic processes having either a flexible belt or a rigiddrum configuration. These electrophotographic imaging members sometimescomprise a photoconductive layer including a single layer or compositelayers. These electrophotographic imaging members take many differentforms. For example, layered photoresponsive imaging members are known inthe art. U.S. Pat. No. 4,265,990 to Stolka et al., which is incorporatedherein by reference in its entirety, describes a layered photoreceptorhaving separate photogenerating and charge transport layers. Thephotogenerating layer disclosed in the 990 patent is capable ofphotogenerating holes and injecting the photogenerated holes into thecharge transport layer. Thus, in the photoreceptors of the 990 patent,the photogenerating material generates electrons and holes whensubjected to light.

More advanced photoconductive photoreceptors containing highlyspecialized component layers are also known. For example, a multilayeredphotoreceptor employed in electrophotographic imaging systems sometimesincludes one or more of a substrate, and undercoating layer, anintermediate layer, an optional hole or charge blocking layer, a chargegenerating layer (including a photogenerating material in a binder) overan undercoating layer and/or a blocking layer, and a charge transportlayer (including a charge transport material in a binder). Additionallayers such as one or more overcoat layer or layers are also sometimesincluded.

In view of such a background, improvement in electrophotographicproperties and durability, miniaturization, reduction in cost, etc., inelectrophotographic photoreceptors have been studied, andelectrophotographic photoreceptors using various materials have beenproposed.

For example, JP-A-63-65449 (the term “JP-A” as used herein means an“unexamined published Japanese patent application”), which isincorporated herein by reference in its entirety, discloses anelectrophotographic photoreceptor in which fine silicone particles areadded to a photosensitive layer, and also discloses that such additionof the fine silicone particles imparts lubricity to a surface of thephotoreceptor.

Further, in forming a photosensitive layer, a method has been proposedin which a charge transfer substance is dispersed in a binder polymer ora polymer precursor thereof, and then the binder polymer or the polymerprecursor thereof is cured. JP-B-5-47104 (the term “JP-B” as used hereinmeans an “examined Japanese patent publication”) and JP-B-60-22347,which are incorporated herein by reference in their entirety, discloseelectrophotographic photoreceptors using silicone materials as thebinder polymers or the polymer precursors thereof.

Furthermore, in order to improve mechanical strength of theelectrophotographic photoreceptor, a protective layer is formed on thesurface of the photosensitive layer in some cases. A crosslinkable resinis used as a material for the protective layer in many cases. However,the protective layer formed by the crosslinkable resin acts as aninsulating layer, which impairs the photoelectric characteristics of thephotoreceptor. For this reason, a method of dispersing a fine conductivemetal oxide powder (JP-A-57-128344) or a charge transfer substance(JP-A-4-15659) in the protective layer and a method of reacting a chargetransfer substance having a reactive functional group with athermoplastic resin to form the protective layer have been proposed.JP-A-57-128344 and JP-A-4-15659 are incorporated herein by reference intheir entirety.

However, even the above-mentioned conventional electrophotographicphotoreceptors are not necessarily sufficient in electrophotographiccharacteristics and durability, particularly when they are used incombination with a charger of the contact charging system (contactcharger) or a cleaning apparatus such as a cleaning blade.

Further, when the photoreceptor is used in combination with the contactcharger and a toner obtained by chemical polymerization (polymerizationtoner), a surface of the photoreceptor is stained with a dischargeproduct produced in contact charging or the polymerization tonerremaining after a transfer step to deteriorate image quality in somecases. Still further, the use of the cleaning blade in order to removethe discharge product adhered to the surface of the photoreceptor or theremaining toner increases friction and abrasion between the surface ofthe photoreceptor and the cleaning blade, resulting in a tendency tocause damage of the surface of the photoreceptor, breakage of the bladeor turning up of the blade.

Furthermore, in producing the electrophotographic photoreceptor, inaddition to improvement in electrophotographic characteristics anddurability, it becomes an important problem to reduce production cost.However, in the case of the conventional electrophotographicphotoreceptor, the problem is encountered that coating defects such asorange peel appearances and hard spots are liable to occur.

The use of silicon-containing compounds in photoreceptor layers,including in photosensitive and protective layers, has been shown toincrease the mechanical lifetime of electrophotographic photoreceptors,under charging conditions and scorotron charging conditions. Forexample, U.S. Patent Application Publication US 2004/0086794 to Yamadaet al., which is incorporated herein by reference in its entirety,discloses a photoreceptor having improved mechanical strength and stainresistance.

However, the above-mentioned conventional electrophotographicphotoreceptor is not necessarily sufficient in electrophotographiccharacteristics and durability, particularly when it is used in anenvironment of high heat and humidity.

Photoreceptors having low wear rates, such as those described in US2004/0086794, also have low refresh rates. The low wear and refreshrates are a primary cause of image deletion errors, particularly underconditions of high humidity and high temperature. U.S. Pat. No.6,730,448 B2 to Yoshino et al., which is incorporated herein byreference in its entirety, addresses this issue in its disclosure ofphotoreceptors having some improvement in image quality, fixing ability,even in an environment of high heat and humidity. However, there stillremains a need for electrophotographic photoreceptors having highmechanical strength and improved electrophotographic characteristics andimproved image deletion characteristics even under conditions of hightemperature and high humidity.

SUMMARY OF THE INVENTION

This invention provides a method for the preparation of an arylaminecompound where the arylamine compound is a symmetric derivative of4-aminobiphenyl. Specifically this invention provides a method whereby aderivative of 4-aminobiphenyl, preferably a symmetric arylaminederivative of 4-aminobiphenyl, can be made using direct hydrogenation ofa precursor organic salt, rather than a longer multi-step synthesisprocedure.

The arylamine derivative of 4-aminobiphenyl is further useful as anintermediate, which could be saponified to produce a dicarboxylic acidsalt of an alkali earth compound. This dicarboxylic acid salt of analkali earth compound can be further derivatized with an alkylhalidecompound containing a siloxane moiety to produce a siloxane containingarylamine compound which is useful in the preparation of siloxanecontaining charge transporting layers for electrophotographicapplication.

These and other features and advantages of various exemplary embodimentsof materials, devices, systems and/or methods according to thisinvention are described in, or are apparent from, the following detaileddescription of the various exemplary embodiments of the methods andsystems according to this invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross sectional view showing a preferredembodiment of an electrophotographic photoreceptor of the invention.

FIG. 2 is a schematic view showing a preferred embodiment of an imageforming apparatus of the invention.

FIG. 3 is a schematic view showing another preferred embodiment of animage forming apparatus of the invention.

FIG. 4 sets forth a process for the production of an arylamineintermediate molecule, Compound B.

FIG. 5 sets forth a process for the production of an arylamine chargetransporting molecule, Compound C.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Preferred embodiments of the invention will be described in detail belowwith reference to drawings in some cases. In the drawings, the samereference numerals and signs are used to designate the same orcorresponding parts, and repeated descriptions are avoided.

Electrophotographic Photoreceptor

In electrophotographic photoreceptors of embodiments, photosensitivelayers comprise one or more silicon compound-containing layers, and thesilicon compound-containing layers further contain resin.

In embodiments, the resin may be a resin soluble in a liquid componentin a coating solution used for formation of this layer. Such a resinsoluble in the liquid component may be selected based upon the kind ofliquid component. For example, if the coating solution contains analcoholic solvent (such as methanol, ethanol or butanol), a polyvinylacetal resin such as a polyvinyl butyral resin, a polyvinyl formal resinor a partially acetalized polyvinyl acetal resin in which butyral ispartially modified with formal or acetoacetal, a polyamide resin, acellulose resin such as ethyl cellulose and a phenol resin may besuitably chosen as the alcohol-soluble resins. These resins may be usedeither alone or as a combination of two or more of them. Of theabove-mentioned resins, the polyvinyl acetal resin is preferred in termsof electric characteristics.

In embodiments, the weight-average molecular weight of the resin solublein the liquid component may be from about 2,000 to about 1,000,000,preferably from about 5,000 to about 50,000. When the average molecularweight is less than 2,000, the effect of enhancing discharge gasresistance, mechanical strength, scratch resistance, particledispersibility, etc., tends to become insufficient. However, when theaverage molecular weight exceeds 1,000,000, the resin solubility in thecoating solution decreases, and the amount of resin added to the coatingsolution may be limited and poor film formation in the production of thephotosensitive layer may result.

Further, the amount of the resin soluble in the liquid component may be,in embodiments, from 0.1 to 15% by weight, or from 0.5 to 10% by weight,based on the total amount of the coating solution. When the amount addedis less than 0.1% by weight, the effect of enhancing discharge gasresistance, mechanical strength, scratch resistance, particledispersibility, etc. tends to become insufficient. However, if theamount of the resin soluble in the liquid component exceeds 15% byweight, there is a tendency for formation of indistinct images when theelectrophotographic photoreceptor of the invention is used at hightemperature and high humidity.

As used herein, a “high temperature environment” or “high temperatureconditions” refer to an atmosphere in which the temperature is at least28-30° C. A “high humidity environment” or “high humidity conditions”refer to an atmosphere in which the relative humidity is at least75-80%.

There is no particular limitation on the silicon compound used inembodiments of the invention, as long as it has at least one siliconatom. However, a compound having two or more silicon atoms in itsmolecule may be used in embodiments. The use of the compound having twoor more silicon atoms in its molecule allows both the strength and imagequality of the electrophotographic photoreceptor to be achieved athigher levels.

In embodiments, at least one member selected from silicon-containingcompounds represented by the following general formulas (2) to (4) andhydrolysates or hydrolytic condensates thereof is preferably used.W¹(—SiR_(3-a)Q_(a))₂  (2)W²(-D-SiR_(3-a)Q_(a))_(b)  (3)SiR_(4-c)Q_(c)  (4)

In general formulas (2) to (4), W¹ represents a divalent organic group,W² represents an organic group derived from a compound having holetransport capability, R represents a member selected from the groupconsisting of a hydrogen atom, an alkyl group and a substituted orunsubstituted aryl group, Q represents a hydrolytic group, D representsa divalent group, a represents an integer of 1 to 3, b represents aninteger of 2 to 4, and c represents an integer of 1 to 4.

R in general formulas (2) to (4) represents a hydrogen atom, an alkylgroup (preferably an alkyl group having 1 to 5 carbon atoms) or asubstituted or unsubstituted aryl group (preferably a substituted orunsubstituted aryl group having 6 to 15 carbon atoms), as describedabove.

Further, the hydrolytic group represented by Q in general formulas (2)to (4) means a functional group which can form a siloxane bond (O—Si—O)by hydrolysis in the curing reaction of the compound represented by anyone of general formulas (2) to (4). Non-limiting examples of thehydrolytic groups that may be used in embodiments include a hydroxylgroup, an alkoxyl group, a methyl ethyl ketoxime group, a diethylaminogroup, an acetoxy group, a propenoxy group and a chloro group. Inparticular embodiments, a group represented by —OR″ (R″ represents analkyl group having 1 to 15 carbon atoms or a trimethylsilyl group) maybe used.

In general formula (3), the divalent group represented by D may be, inembodiments, a divalent hydrocarbon group represented by —C_(n)H_(2n)—,—C_(n)H_(2n-2)—, —C_(n)H_(2n-4)— (n is an integer of 1 to about 15, andpreferably from 2 to about 10), —CH₂—C₆H₄— or —C₆H₄—C₆H₄—, anoxycarbonyl group (—COO—), a thio group (—S—), an oxy group (—O—), anisocyano group (—N═CH—) or a divalent group in which two or more of themare combined. The divalent group may have a substituent group such as analkyl group, a phenyl group, an alkoxyl group or an amino group on itsside chain. When D is the above-mentioned preferred divalent group,proper flexibility may be imparted to an organic silicate skeleton,thereby tending to improve the strength of the layer.

Non-limiting examples of the compounds represented by theabove-mentioned general formula (2) are shown in Table 1. TABLE 1 No.Structural Formula III-1 (MeO)₃Si—(CH₂)₂—Si(OMe)₃ III-2(MeO)₂Me—(CH₂)₂—SiMe(OMe)₂ III-3 (MeO)₂MeSi—(CH₂)₆—SiMe(OMe)₂ III-4MeO)₃Si—(CH₂)₆—Si(OMe)₃ III-5 (EtO)₃Si—(CH₂)₆—Si(OEt)₃ III-6(MeO)₂MeSi—(CH₂)₁₀—SiMe(OMe)₂ III-7 (MeO)₃Si—(CH₂)₃—NH—(CH₂)₃—Si(OMe)₃III-8 (MeO)₃Si—(CH₂)₃—NH—(CH₂)₂—NH—(CH₂)₃—Si(OMe)₃ III-9

III-10

III-11

III-12

III-13

III-14

III-15 (MeO)₃SiC₃H₆—O—CH₂CH{—O—C₃H₆Si(OMe)₃}—CH₂{—O—C₃H₆Si(OMe)₃} III-16(MeO)₃SiC₂H₄—SiMe₂—O—SiMe₂—O—SiMe₂—C₂H₄Si(OMe)₃

Further, in the above-mentioned general formula (3), there is noparticular limitation on the organic group represented by W², as long asit is a group having hole transport capability. However, in particularembodiments, W² may be an organic group represented by the followinggeneral formula (6):

wherein Ar¹, Ar², Ar³ and Ar⁴, which may be the same or different, eachrepresents a substituted or unsubstituted aryl group, Ar⁵ represents asubstituted or unsubstituted aryl or arylene group, k represents 0 or 1,and at least one of Ar¹ to Ar⁵ has a bonding hand to connect with-D-SiR_(3-a)Q_(a) in general formula (3).

Ar¹ to Ar⁴ in the above-mentioned general formula (6) are eachpreferably any one of the following formulas (7) to (13):

In formulas (7) to (13), R⁶ represents a member selected from the groupconsisting of a hydrogen atom, an alkyl group having 1 to 4 carbonatoms, an unsubstituted phenyl group or a phenyl group substituted by analkyl group having 1 to 4 carbon atoms or an alkoxyl group having 1 to 4carbon atoms, and an aralkyl group having 7 to 10 carbon atoms; R⁷ to R⁹each represents a member selected from the group consisting of ahydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxylgroup having 1 to 4 carbon atoms, an unsubstituted phenyl group or aphenyl group substituted by an alkoxyl group having 1 to 4 carbon atoms,an aralkyl group having 7 to 10 carbon atoms, and a halogen atom; Arrepresents a substituted or unsubstituted arylene group; X represents-D-SiR_(3-a)Q_(a) in general formula (3); m and s each represents 0 or1; q and r each represents an integer of 1 to 10; and t and t′ eachrepresents an integer of 1 to 3.

Here, Ar in formula (7) may be one represented by the following formula(14) or (15):

In formulas (14) and (15), R¹⁰ and R¹¹ each represent a member selectedfrom the group consisting of a hydrogen atom, an alkyl group having 1 to4 carbon atoms, an alkoxyl group having 1 to 4 carbon atoms, anunsubstituted phenyl group or a phenyl group substituted by an alkoxylgroup having 1 to 4 carbon atoms, an aralkyl group having 7 to 10 carbonatoms, and a halogen atom; and t represents an integer of 1 to 3.

Further, Z′ in formula (13) is preferably one represented by any one ofthe following formulas (16) to (23):

In formulas (16) to (23), R¹² and R¹³ each represent a member selectedfrom the group consisting of a hydrogen atom, an alkyl group having 1 to4 carbon atoms, an alkoxyl group having 1 to 4 carbon atoms, anunsubstituted phenyl group or a phenyl group substituted by an alkoxylgroup having 1 to 4 carbon atoms, an aralkyl group having 7 to 10 carbonatoms, and a halogen atom; W represents a divalent group; q and r eachrepresents an integer of 1 to 10; and t represents an integer of 1 to 3.

W in the above-mentioned formulas (22) and (23) may be any one ofdivalent groups represented by the following formulas (24) to (32):

In formula (31), u represents an integer of 0 to 3.

Further, in general formula (6), Ar⁵ is the aryl group illustrated inthe description of Ar¹ to Ar⁴, when k is 0, and an arylene groupobtained by removing a certain hydrogen atom from such an aryl group,when k is 1.

Combinations of Ar^(l), Ar², Ar³, Ar⁴, Ar⁵ and integer k in formula (6)and a group represented by -D-SiR_(3-a)Q_(a) in general formula (3) inparticular exemplary embodiments are shown in Tables 2; additionalexemplary embodiments can be found in US 2004/0086794 and U.S. Pat. No.6,730,448 B2, the entire disclosures of which are incorporated herein byreference. In the tables, S represents -D-SiR_(3-a)Q_(a) linked to Ar¹to Ar⁵, Me represents a methyl group, Et represents an ethyl group, andPr represents a propyl group. TABLE 2 Ar³ No. Ar¹ Ar² & Ar⁴ Ar⁵ k —S V-1

—

O —(CH₂)₂—COO—(CH₂)₃—Si(O^(i)Pr)₃ V-2

—

O —(CH₂)₂—COO—(CH₂)₃—SiMe(O^(i)Pr)₂ V-3

—

O —(CH₂)₂—COO—(CH₂)₃—SiMe₂(O^(i)Pr) V-4

—

O —COO—(CH₂)₃—Si(O^(i)Pr)₃ V-5

—

O —(CH₂)₂—COO—(CH₂)₃—Si(O^(i)Pr)₃ V-6

—

O —(CH₂)₂—COO—(CH₂)₃—SiMe(O^(i)Pr)₂ V-7

—

O —(CH₂)₂—COO—(CH₂)₃—SiMe₂(O^(i)Pr) V-8

—

O —COO—(CH₂)₃—Si(O^(i)Pr)₃ V-9

—

O —(CH₂)₂—COO—(CH₂)₃—Si(O^(i)Pr)₃ V-10

—

O —(CH₂)₂—COO—(CH₂)₃—SiMe(O^(i)Pr)₂ V-11

—

O —(CH₂)₂—COO—(CH₂)₃—SiMe₂(O^(i)Pr) V-12

—

O —COO—(CH₂)₃—Si(O^(i)Pr)₃ V-13

—

O —(CH₂)₂—COO—(CH₂)₃—Si(O^(i)Pr)₃ V-14

—

O —(CH₂)₂—COO—(CH₂)₃—SiMe(O^(i)Pr)₂ V-15

—

O —(CH₂)₂—COO—(CH₂)₃—SiMe₂(O^(i)Pr) V-16

—

O —COO—(CH₂)₃—Si(O^(i)Pr)₃

Further, in embodiments, the silicon compounds represented by theabove-mentioned general formula (4) may include silane coupling agentssuch as a tetrafunctional alkoxysilane (c=4) such as tetramethoxysilaneor tetraethoxysilane; a trifunctional alkoxysilane (c=3) such asmethyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane,methyltrimethoxyethoxysilane, vinyltrimethoxysilane,vinyltriethoxysilane, phenyltrimethoxysilane,γ-glycidoxypropylmethyldiethoxysilane,γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane,γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane,γ-aminopropylmethyldimethoxysilane,N-β-(aminoethyl)-γ-aminopropyltriethoxysilane,(tridecafluoro-1,1,2,2-tetrahydrooctyl)triethoxysilane,(3,3,3-trifluoropropyl)trimethoxysilane,3-(heptafluoroisopropoxy)propyltriethoxysilane,1H,1H,2H,2H-perfluoroalkyltriethoxysilane,1H,1H,2H,2H-perfluorodecyltriethoxysilane or1H,1H,2H,2H-perfluorooctyltriethoxysilane; a bifunctional alkoxysilane(c=2) such as dimethyldimethoxysilane, diphenyldimethoxysilane ormethylphenyldimethoxysilane; and a monofunctional alkoxysilane (c=1)such as trimethylmethoxysilane.

In order to improve the strength of the photosensitive layer, thetrifunctional alkoxysilanes and the tetrafunctional alkoxysilanes may beused in embodiments, and in order to improve the flexibility and filmforming properties, the monofunctional alkoxysilanes and thebifunctional alkoxysilanes may be used in embodiments.

Silicone hard coating agents containing these coupling agents can alsobe used in embodiments. Commercially available hard coating agentsinclude KP-85, X-40-99740 and X-40-2239 (available from ShinetsuSilicone Co., Ltd.), and AY42-440, AY42-441 and AY49-208 (available fromToray Dow Corning Co., Ltd.).

In embodiments, the silicon compound-containing layer may contain eitheronly one of the silicon compounds represented by the above-mentionedgeneral formulas (2) and (4) or two or more of them. Further, thecompounds represented by general formulas (2) to (4) may include amonofunctional compound (a compound in which a or c is 1), abifunctional compound (a compound in which a or c is 2), a trifunctionalcompound (a compound in which a or c is 3) and a tetrafunctionalcompound (a compound in which a or c is 4). However, in particularembodiments, the number of silicon atoms derived from thesilicon-containing compounds represented by the above-mentioned generalformulas (2) to (4) in the silicon compound-containing layer satisfiesthe following equation (5):(N_(a=3)+N_(c≧3))/N_(total)≦0.5  (5)wherein N_(a=3) represents the number of silicon atoms derived from—SiR_(3-a)Q_(a) of the silicon compound represented by general formula(2) or (3) in which a is 3, N_(c≧3) represents the number of siliconatoms derived from the silicon compound represented by general formula(4) in which c is 3 or 4, and N_(total) represents the total of thenumber of silicon atoms derived from —SiR_(3-a)Q_(a) of the siliconcompound represented by general formula (2) or (3) and the number ofsilicon atoms derived from the silicon compound represented by generalformula (4). That is to say, the ratio of the silicon compoundscontained is preferably set so that the number of silicon atoms derivedfrom the trifunctional compound or the tetrafunctional compound becomes0.5 or less based on the number of silicon atoms derived from thesilicon-containing compounds represented by general formulas (2) to (4)(in the case of the compound represented by general formula (2) or (3),the silicon atoms are limited to ones derived from —SiR_(3-a)Q_(a), andthe same applies hereinafter). When the value of the left side ofequation (5) exceeds 0.5, an indistinct image tends to be liable tooccur at high temperature and high humidity. When the value of the leftside of equation (5) is decreased, there is the possibility that itcauses a decrease in strength. However, the use of the compound havingtwo or more silicon atoms in its molecule can improve the strength.

In order to further improve the stain adhesion resistance and lubricityof embodiments of the electrophotographic photoreceptor, various fineparticles can also be added to the silicon compound-containing layer.The fine particles may be used either alone or as a combination of twoor more of them. Non-limiting examples of the fine particles includefine particles containing silicon, such as fine particles containingsilicon as a constituent element, and specifically include colloidalsilica and fine silicone particles.

Colloidal silica used in embodiments as the fine particles containingsilicon in the invention is selected from an acidic or alkaline aqueousdispersion of the fine particles having an average particle size of 1 to100 nm, or 10 to 30 nm, and a dispersion of the fine particles in anorganic solvent such as an alcohol, a ketone or an ester, and generally,commercially available particles can be used.

There is no particular limitation on the solid content of colloidalsilica in a top surface layer of the electrophotographic photoreceptorof embodiments of the invention. However, in embodiments, colloidalsilica is used within the range of from about 1 to about 50% by weight,preferably from about 5 to about 30% by weight, based on the total solidcontent of the top surface layer, in terms of film forming properties,electric characteristics and strength.

The fine silicone particles used as the fine particles containingsilicon in the invention are selected from silicone resin particles,silicone rubber particles and silica particles surface-treated withsilicone, which are spherical and have an average particle size of fromabout 1 to 500 nm, preferably from about 10 to about 100 nm, andgenerally, commercially available particles can be used in embodiments.

In embodiments, the fine silicone particles are small-sized particlesthat are chemically inactive and excellent in dispersibility in a resin,and further are low in content as may be necessary for obtainingsufficient characteristics. Accordingly, the surface properties of theelectrophotographic photoreceptor can be improved without inhibition ofthe crosslinking reaction. That is to say, fine silicone particlesimprove the lubricity and water repellency of surfaces ofelectrophotographic photoreceptors where incorporated into strongcrosslinked structures, which may then be able to maintain good wearresistance and stain adhesion resistance for a long period of time. Thecontent of the fine silicone particles in the siliconcompound-containing layer of embodiments may be within the range of fromabout 0.1 to about 20% by weight, preferably from about 0.5 to about 10%by weight, based on the total solid content of the siliconcompound-containing layer.

Other fine particles that may be used in embodiments of the inventioninclude fine fluorine-based particles such as ethylene tetrafluoride,ethylene trifluoride, propylene hexafluoride, vinyl fluoride andvinylidene fluoride, and semiconductive metal oxides such as ZnO—Al₂O₃,SnO₂—Sb₂O₃, In₂O₃—SnO₂, ZnO—TiO₂, MgO—Al₂O₃, FeO—TiO₂, TiO₂, SnO₂,In₂O₃, ZnO and MgO.

In conventional electrophotographic photoreceptors, when theabove-mentioned fine particles are contained in the photosensitivelayer, the compatibility of the fine particles with a charge transfersubstance or a binding resin may become insufficient, which causes layerseparation in the photosensitive layer, and thus forms an opaque film.As a result, the electric characteristics have deteriorated in somecases. In contrast, the silicon compound-containing layer of embodiments(a charge transfer layer in this case) may contain the resin soluble inthe liquid component in the coating solution used for formation of thislayer and the silicon compound, thereby improving the dispersibility ofthe fine particles in the silicon compound-containing layer.Accordingly, the pot life of the coating solution can be sufficientlyprolonged, and it becomes possible to prevent deterioration of theelectric characteristics.

Further, an additive such as a plasticizer, a surface modifier, anantioxidant, or an agent for preventing deterioration by light can alsobe used in the silicon compound-containing layer of embodiments.Non-limiting examples of plasticizers that may be used in embodimentsinclude, for example, biphenyl, biphenyl chloride, terphenyl, dibutylphthalate, diethylene glycol phthalate, dioctyl phthalate,triphenylphosphoric acid, methylnaphthalene, benzophenone, chlorinatedparaffin, polypropylene, polystyrene and various fluorohydrocarbons.

The antioxidants may include an antioxidant having a hindered phenol,hindered amine, thioether or phosphite partial structure. This iseffective for improvement of potential stability and image quality inenvironmental variation. The antioxidants include an antioxidant havinga hindered phenol, hindered amine, thioether or phosphite partialstructure. This is effective for improvement of potential stability andimage quality in environmental variation. For example, the hinderedphenol antioxidants include Sumilizer BHT-R, Sumilizer MDP-S, SumilizerBBM-S, Sumilizer WX-R, Sumilizer NW, Sumilizer BP-76, Sumilizer BP-101,Sumilizer GA-80, Sumilizer GM and Sumilizer GS (the above aremanufactured by Sumitomo Chemical Co., Ltd.), IRGANOX 1010, IRGANOX1035, IRGANOX 1076, IRGANOX 1098, IRGANOX 1135, IRGANOX 1141, IRGANOX1222, IRGANOX 1330, IRGANOX 1425WLj, IRGANOX 1520Lj, IRGANOX 245,IRGANOX 259, IRGANOX 3114, IRGANOX 3790, IRGANOX 5057 and IRGANOX 565(the above are manufactured by Ciba Specialty Chemicals), and AdecastabAO-20, Adecastab AO-30, Adecastab AO-40, Adecastab AO-50, AdecastabAO-60, Adecastab AO-70, Adecastab AO-80 and Adecastab AO-330i (the aboveare manufactured by Asahi Denka Co., Ltd.). The hindered amineantioxidants include Sanol LS2626, Sanol LS765, Sanol LS770, SanolLS744, Tinuvin 144, Tinuvin 622LD, Mark LA57, Mark LA67, Mark LA62, MarkLA68, Mark LA63 and Sumilizer TPS, and the phosphite antioxidantsinclude Mark 2112, Mark PEP•8, Mark PEP•24G, Mark PEP•36, Mark 329K andMark HP•10. Of these, the hindered phenol and hindered amineantioxidants are particularly preferred.

There is no particular limitation on the thickness of thesilicon-containing layer, however, in embodiments, thesilicon-containing layer may be in the range from about 2 to about 5 μmin thickness, preferably from about 2.7 to about 3.2 μm in thickness.

In embodiments of the invention, the photosensitive layer may comprisethe silicon compound-containing layer as described above. Inembodiments, the photosensitive has a peak area in the region of −40 to0 ppm (S₁) and a peak area in the region of −100 to −50 ppm (S₂) in a²⁹Si—NMR spectrum that satisfy the following equation (1):S ₁/(S ₁ +S ₂)≧0.5  (1)When S₁/(S₁+S₂) is less than 0.5, defects are liable to occur. Inparticular, there is a tendency to cause an indistinct image at hightemperature and the pot life shortened. Thus, S₁/(S₁+S₂) may be about0.6 or more, preferably about 0.7 or more.

The ²⁹Si—NMR spectrum of the photosensitive layer can be measuredthrough the following procedure. First, the photosensitive layer isseparated from the electrophotographic photoreceptor by use of asilicon-free adhesive tape, and a sample tube (7 mm in diameter) made ofzirconia is filled with 150 mg of the resulting separated product. Thesample tube is set on a ²⁹Si—NMR spectral measuring apparatus (forexample, UNITY-300 manufactured by Varian, Inc.), and measurements aremade under the following conditions:

Frequency: 59.59 MHz;

Delay time: 10.00 seconds;

Contact time: 2.5 milliseconds;

Measuring temperature: 25° C.;

Integrating number: 10,000 times; and

Revolution: 4,000±500 rpm.

The electrophotographic photoreceptor of embodiments may be either afunction-separation-type photoreceptor, in which a layer containing acharge generation substance (charge generation layer) and a layercontaining a charge transfer substance (charge transfer layer) areseparately provided, or a monolayer-type photoreceptor, in which boththe charge generation layer and the charge transfer layer are containedin the same layer, as long as the electrophotographic photoreceptor ofthe particular embodiment has the photosensitive layer provided with theabove-mentioned silicon compound-containing layer. Theelectrophotographic photoreceptor of the invention will be described ingreater detail below, taking the function-separation-type photoreceptoras an example.

FIG. 1 is a cross-sectional view schematically showing an embodiment ofthe electrophotographic photoreceptor of the invention. Theelectrophotographic photoreceptor 1 shown in FIG. 1 is afunction-separation-type photoreceptor in which a charge generationlayer 13 and a charge transfer layer 14 are separately provided. Thatis, an underlayer 12, the charge generation layer 13, the chargetransfer layer 14 and a protective layer 15 are laminated onto aconductive support 11 to form a photosensitive layer 16. The protectivelayer 15 contains a resin soluble in the liquid component contained inthe coating solution used for formation of this layer and the siliconcompound. Further, a peak area in the region of −40 to 0 ppm and a peakarea in the region of −100 to −50 ppm in a ²⁹Si—NMR spectrum of thephotosensitive layer 16 satisfy equation (1).

The conductive support 11 may include, for example, a metal plate, ametal drum or a metal belt using a metal such as aluminum, copper, zinc,stainless steel, chromium, nickel, molybdenum, vanadium, indium, gold ora platinum, or an alloy thereof; and paper or a plastic film or beltcoated, deposited or laminated with a conductive polymer, a conductivecompound such as indium oxide, a metal such as aluminum, palladium orgold, or an alloy thereof. Further, surface treatment (such as anodicoxidation coating, hot water oxidation, chemical treatment, or coloring)or diffused reflection treatment (such as graining) can also be appliedto a surface of the support 11.

Binding resins used in the underlayer 12 of embodiments may include butare not limited to, one or more polyamide resins, vinyl chloride resins,vinyl acetate resins, phenol resins, polyurethane resins, melamineresins, benzoguanamine resins, a polyimide resins, polyethylene resins,polypropylene resins, polycarbonate resins, acrylic resins, methacrylicresins, vinylidene chloride resins, polyvinyl acetal resins, vinylchloride-vinyl acetate copolymers, polyvinyl alcohol resins, awater-soluble polyester resins, nitrocelluloses, caseins, gelatins,polyglutamic acids, starches, starch acetates, amino starches,polyacrylic acids, polyacrylamides, zirconium chelate compounds, titanylchelate compounds, titanyl alkoxide compounds, organic titanylcompounds, silane coupling agents and mixtures thereof. Further, fineparticles of titanium oxide, aluminum oxide, silicon oxide, zirconiumoxide, barium titanate, a silicone resin or the like may be added to theabove-mentioned binding resin in embodiments.

As a coating method in forming the underlayer of embodiments, anordinary method such as blade coating, Mayer bar coating, spray coating,dip coating, bead coating, air knife coating or curtain coating may beemployed. The thickness of the underlayer may be from about 0.01 toabout 40 μm.

Non-limiting examples of charge generation substances that may becontained in the charge generation layer 13 of embodiments include, butare not limited to, various organic pigments and organic dyes; such asazo pigments, quinoline pigments, perylene pigments, indigo pigments,thioindigo pigments, bisbenzimidazole pigments, phthalocyanine pigments,quinacridone pigments, quinoline pigments, lake pigments, azo lakepigments, anthraquinone pigments, oxazine pigments, dioxazine pigments,triphenylmethane pigments, azulenium dyes, squalium dyes, pyrylium dyes,triallylmethane dyes, xanthene dyes, thiazine dyes and cyanine dyes; andinorganic materials such as amorphous silicon, amorphous selenium,tellurium, selenium-tellurium alloys, cadmium sulfide, antimony sulfide,zinc oxide and zinc sulfide. In embodiments, cyclocondensed aromaticpigments, perylene pigments and azo pigments may be used to impartsensitivity, electric stability and photochemical stability againstirradiated light. These charge generation substances may be used eitheralone or as a combination of two or more.

In embodiments, the charge generation layer 13 may be formed by vacuumdeposition of the charge generation substance or application of acoating solution in which the charge generation substance is dispersedin an organic solvent containing a binding resin. The binding resinsused in the charge generation layer of embodiments include polyvinylacetal resins such as polyvinyl butyral resins, polyvinyl formal resinsor partially acetalized polyvinyl acetal resins in which butyral ispartially modified with formal or acetoacetal, polyamide resins,polyester resins, modified ether type polyester resins, polycarbonateresins, acrylic resins, polyvinyl chloride resins, polyvinylidenechlorides, polystyrene resins, polyvinyl acetate resins, vinylchloride-vinyl acetate copolymers, silicone resins, phenol resins,phenoxy resins, melamine resins, benzoguanamine resins, urea resins,polyurethane resins, poly-N-vinylcarbazole resins, polyvinylanthraceneresins, polyvinylpyrene resins and mixtures thereof. In embodiments inwhich one or more of polyvinyl acetal resins, vinyl chloride-vinylacetate copolymers, phenoxy resins or modified ether type polyesterresins are used, the dispersibility of the charge generation substancemay be improved to cause no occurrence of coagulation of the chargegeneration substance, and a coating solution that is stable for a longperiod of time may be obtained. The use of such a coating solution inembodiments makes it possible to form a uniform coating easily andsurely. As a result, the electric characteristics may be improved, andimage defects may be prevented. Further, the compounding ratio of thecharge generation substance to the binding resin may be, in embodiments,within the range of from about 5:1 to about 1:2 by volume ratio.

Further, the solvents used in preparing the coating solution inembodiments may include organic solvents such as methanol, ethanol,n-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethylcellosolve, acetone, methyl ethyl ketone, cyclohexanone, chlorobenzene,methyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylenechloride, chloroform and mixtures thereof.

Methods for applying the coating solution in embodiments include thecoating methods described above with reference to the underlayer. Thethickness of the charge generation layer 13 thus formed may be fromabout 0.01 to about 5 μm, preferably from about 0.1 to about 2 μm. Whenthe thickness of the charge generation layer 13 is less than 0.01 μm, itbecomes difficult to uniformly form the charge generation layer. On theother hand, when the thickness exceeds 5 μm, the electrophotographiccharacteristics tend to significantly deteriorate.

Further, a stabilizer such as an antioxidant or an inactivating agentcan also be added to the charge generation layer 13 in embodiments.Non-limiting examples of antioxidants that may be used include but arenot limited to antioxidants such as phenolic, sulfur, phosphorus andamine compounds. Inactivating agents that may be used in embodiments mayinclude bis(dithiobenzyl)nickel and nickel di-n-butylthiocarbamate.

In embodiments, the charge transfer layer 14 can be formed by applying acoating solution containing the charge transfer substance and a bindingresin, and further fine particles, an additive, etc., as describedabove.

Low molecular weight charge transfer substances that may be used inembodiments may include, for example, pyrene, carbazole, hydrazone,oxazole, oxadiazole, pyrazoline, arylamine, arylmethane, benzidine,thiazole, stilbene and butadiene compounds. In embodiments, highmolecular weight charge transfer substances may be used and include, forexample, poly-N-vinylcarbazoles, poly-N-vinylcarbazole halides,polyvinyl pyrenes, polyvinylanthracenes, polyvinylacridines,pyrene-formaldehyde resins, ethylcarbazole-formaldehyde resins,triphenylmethane polymers and polysilanes. Triphenylamine compounds,triphenylmethane compounds and benzidine compounds may be used inembodiments to promote mobility, stability and transparency to light.Further, silicon compound represented by general formula (2) can also beused as charge transfer substances in particular embodiments.

As binding resins in embodiments, high molecular weight polymers thatcan form an electrical insulating film may be used. For example, whenpolyvinyl acetal resins, polyamide resins, cellulose resins, phenolresins, etc., which are soluble in alcoholic solvents, are used, bindingresins used together with these resins include polycarbonates,polyesters, methacrylic resins, acrylic resins, polyvinyl chlorides,polyvinylidene chlorides, polystyrenes, polyvinyl acetates,styrene-butadiene copolymers, vinylidene chloride-acrylonitrilecopolymers, vinyl chloride-vinyl acetate copolymers, vinylchloride-vinyl acetate-maleic anhydride copolymers, silicone resins,silicone-alkyd resins, phenol-formaldehyde resins, styrene-alkyd resins,poly-N-vinylcarbazoles, polyvinyl butyrals, polyvinyl formals,polysulfones, casein, gelatin, polyvinyl alcohols, phenol resins,polyamides, carboxymethyl celluloses, vinylidene chloride-based polymerlatexes and polyurethanes. Of the above-mentioned high molecular weightpolymers, polycarbonates, polyesters, methacrylic resins and acrylicresins have excellent compatibility with the charge transfer substance,solubility and strength.

The charge transfer layer 14 of embodiments may further contain anadditive such as a plasticizer, a surface modifier, an antioxidant or anagent for preventing deterioration by light.

The thickness of the charge transfer layer 14 may be, in embodiments,from about 5 to about 50 μm, preferably from about 10 to about 40 μm.When the thickness of the charge transfer layer is less than 5 μm,charging becomes difficult. However, thicknesses exceeding 50 μm resultsignificant deterioration of the electrophotographic characteristics.

Protective layer 15 may contain, in embodiments, resins soluble inliquid components in coating solution used for formation of protectivelayers and silicon compounds as described above. Protective layer 15 mayfurther contain a lubricant or fine particles of a silicone oil or afluorine material, which can also improve lubricity and strength.Non-limiting examples of the lubricants include the above-mentionedfluorine-based silane coupling agents. Fine particles to be dispersed inthe protective layer 15 of embodiments may include fine particlescomprising resins obtained by copolymerizing fluororesins with hydroxylgroup-containing monomers, as described in Proceedings of Lectures inthe Eighth Polymer Material Forum, page 89, and semiconductive metaloxides, as well as the above-mentioned fine silicone particles and finefluorine-based particles. The thickness of the protective layer may be,in embodiments, from about 0.1 to about 10 μm, preferably from about 0.5to about 7 μm.

The electrophotographic photoreceptor of embodiments should not beconstrued as being limited to the abovementioned constitution. Forexample, the electrophotographic photoreceptor shown in FIG. 1 isprovided with the protective layer 15. However, when the charge transferlayer 14 contains the resin soluble in the liquid component in thecoating solution used for formation of this layer and the siliconcompound, the charge transfer layer 14 may be used as a top surfacelayer (a layer on the side farthest apart from the support 11) withoutusing the protective layer 15. In this case, the charge transfersubstance contained in the charge transfer layer 14 is preferablysoluble in the liquid component in the coating solution used forformation of the charge transfer layer 14. For example, when the coatingsolution used for formation of the charge transfer layer 14 contains thealcoholic solvent, the silicon compounds represented by theabove-mentioned general formula (2) and compounds represented by thefollowing formulas (VI-1) to (VI-16) are preferably used as the chargetransfer substances.

Other exemplary charge transport molecules include, but are not limitedto, the various compounds identified above as the organic group W²,which have hole transport capability. In embodiments, a particularlypreferred charge transport molecule is the arylamine of formula (33):

Production of such arylamine charge transport compounds, however, isgenerally a costly, time-consuming, multi-step process.

A process for producing this and other similar intermediate products isto utilize a direct hydrogenation reaction on an organic salt, in theprocess of converting a first disubstituted 4-aminobiphenyl compoundinto a second disubstituted 4-aminobiphenyl compound.

In a first step, a suitable first disubstituted 4-aminobiphenyl compound(shown as Compound A in FIG. 4) is formylated by means of a Vilsmeier(or Vilsmeier-Haack) reaction, to form a bisformyl substituted compound.Those skilled in the art will recognize there may be other ways andmethods for the introduction of a formyl group into a compound of thistype, for example by treatment of a halogenated derivative of the firstdisubstituted 4-aminobiphenyl compound (Compound A) with n-butyllithiumfollowed by dimethylformamide (DMF) or treatment of such a compound withhexamethylene tetraamine in the presence of trifluoroacetic acid. Onesuitable method for forming bisformyl substituted compounds is disclosedin U.S. patent application Ser. No. 10/909,136 filed Jul. 30, 2004, theentire disclosure of which is incorporated herein by reference.Accordingly, neither the Vilsmeier (or Vilsmeier-Haack) reaction nor then-butyllithium treatment nor the hexamethylene tetraamine treatment ismeant to be an exhaustive list. Suitable examples of the firstdisubstituted 4-aminobiphenyl compound include, for example, compoundsof the following general formula (34):4-aminobiphenyl-(R¹)(R²)  (34)where R¹ and R², which can be the same or different, represent aromaticor heterocyclic groups. Suitable aromatic groups include, for example,substituted or unsubstituted phenyl groups; substituted or unsubstitutedgroups including two or more phenyl groups, such as biphenyl groups,triphenyl groups, and the like; substituted or unsubstituted fusedpolycyclic hydrocarbons, for example having from 2 to about 10 fusedbenzene rings, such as naphthyl groups, anthryl groups, phenanthrylgroups, pyrenyl groups, and the like; and mixtures thereof. Suitableheterocyclic groups include, for example, substituted or unsubstituted3- to 10-membered rings (preferably 5- or 6-membered rings) containingone or more heteroatoms, such as oxygen, sulfur, selenium, tellurium,nitrogen, phosphorus, arsenic, antimony, bismuth, silicon, germanium,tin, lead and mercury. Examples of such heterocyclic groups include, forexample, substituted or unsubstituted groups selected from thiophene,pyridine, diazine, triazine, and the like. Substitution of these groupscan be at one or more locations on the aromatic or heterocyclic ring(s),and can be by, for example, an alkyl groups of from 1 to about 15 carbonatoms, an alkenyl groups of from 1 to about 15 carbon atoms, alkynylgroups of from 1 to about 15 carbon atoms, halogen atoms, acid groups,ester groups, and the like. It will be appreciated by those skilled inthe art that other compounds can also be used to provide a desiredarylamine, and the invention is not limited to the above-listedcompounds.

The first disubstituted 4-aminobiphenyl compound is subjected to aVilsmeier reaction, to form a bisformyl substituted compound. Suchformylation reactions are generally well known in the art, and thus arenot described in detail herein. For example,N,N-diphenyl-4-aminobiphenyl can be formylated (bisformylated) byreacting the compound with dimethylformamide (DMF) and phosphorusoxychloride (POCl₃). The result is a compound of the following generalformula (35):4-aminobiphenyl-(R¹—CH═O)(R²—CH═O)  (35)where R¹ and R² are as described above.

Of course, it will be recognized by those skilled in the art that theformylating reaction step can be omitted, where the first disubstituted4-aminobiphenyl compound is already a bisformyl substituted compound.Thus, the formylating step is optional in those embodiments where thestarting material is a formylated compound, but may be necessary wherethe starting material is not a formylated compound.

In a second step, the bisformylated compound of the first step issubjected to a condensation or modification reaction, preferably toconvert the formyl end groups into acid groups. For example, thebisformylated compound of the first step can be subjected to aKnoevenagel condensation reaction, or specifically to a Doebnermodification condensation reaction, to convert the —CH═O formyl endgroups into —C═C—COOH carboxylic acid end groups. In embodiments, theKnoevenagel condensation reaction can be conducted by reaction of thebisformylated compound with an active methylene compound in the presenceof an ammonia or an amine. Such Knoevenagel condensation reactions arealso generally well known in the art, and thus are not described indetail herein.

A preferred active methylene compound is a malonic acid or ester, suchas malonic acid. For toxicity reasons and ease of handling a preferredamine is piperidine, although ammonia, pyridine, and the like can alsobe used. The reaction can be conducted in a suitable solvent, such astoluene. Although the resultant acidified compound can be isolated fromthe reactants and solvent following completion of the reaction, suchseparation is not required. Thus, for example, in embodiments it ispreferred that the reaction product mixture of the second step is useddirectly in the succeeding third step, described below, withoutpurification or isolation.

In a third step, a hydrogenation reaction is used to directly and mildlyhydrogenate unsaturated double bonds in the bisorganic salt compound,which in the preferred embodiments is a bispiperidine salt, produced inthe second step. Such direct hydrogenation can be conducted in thepresence of a suitable catalyst, such as a rhodium, palladium, platinum,raney nickel, or the like catalyst. The catalyst can be supported on asubstrate, such as a carbon substrate, if desired. In embodiments, a 10%palladium on wet carbon catalyst is preferred.

For example, in one embodiment, the direct hydrogenation process can beperformed under relatively low pressures of hydrogen gas, such asbetween 1 and 5 atmospheres, preferably between 1 and 2 atmospheres.After suitable reaction time, the absence of unsaturated double bondscan be confirmed, such as by using UV-Vis (ultraviolet visible)spectroscopy (where A_(375 nm)=0) or by 1H NMR spectroscopy (CDCl3)indicating the absence of proton resonances for the protons on theunsaturated double bond (in the range of 6.0-6.8 ppm). The freesaturated dicarboxylic acid can be freed from its piperidine salt bytreatment of its solution with a suitable aqueous protic acid such ashydrochloric acid, nitric acid, sulfuric acid, or the like. For example,it has been found that the free dicarboxylic acid can discolor with timeand exposure to air, so it is immediately converted to a salt of analkali earth. Suitable alkali earths include, for example, lithium,sodium, potassium, rubidium, cesium, and francium, with potassium beingpreferred. In a preferred embodiment, the free dicarboxylic acid istreated with potassium methoxide or potassium isopropoxide in analcoholic solution, the dicarboxylic acid is freely soluble in alcoholswhereas the dipotassium salt is not.

The result of the process of the present invention is the formation of adesired arylamine compound, which can broadly be characterized as aderivative of 4-aminobiphenyl. Thus, for example, the arylaminecompounds provided by the present invention can be represented by thefollowing general formula (36):4-aminobiphenyl-(R¹—CH₂—CH₂—COO⁻X₁ ⁺)(R²—CH₂—CH₂—COO—X₂ ⁺)  (36)where R¹ and R², which can be the same or different, are as describedabove, and X₁ and X₂, which can be the same or different, are cationicgroups, such as hydrogen ions (H⁺), potassium ions (K⁺), or the like.

After each step in the process, suitable separation, filtration, andpurification processes can be conducted, as desired. For example, afterthe third step, the final product can be isolated, for example, by asuitable recrystallization procedure. All of these procedures areconventional and will be apparent to those skilled in the art. However,a benefit of the invention, as described above, is that the reactionproduct mixture from the second step can be directly used in the thirdstep without isolation or purification.

Image Forming Apparatus and Process Cartridge

FIG. 2 is a schematic view showing an embodiment of an image formingapparatus. In the apparatus shown in FIG. 2, the electrophotographicphotoreceptor 1 constituted as shown in FIG. 1 is supported by a support9, and rotatable at a specified rotational speed in the directionindicated by the arrow, centered on the support 9. A contact chargingdevice 2, an exposure device 3, a developing device 4, a transfer device5 and a cleaning unit 7 are arranged in this order along the rotationaldirection of the electrophotographic photoreceptor 1. Further, thisexemplary apparatus is equipped with an image fixing device 6, and amedium P to which a toner image is to be transferred is conveyed to theimage fixing device 6 through the transfer device 5.

The contact charging device 2 has a roller-shaped contact chargingmember. The contact charging member is arranged so that it comes intocontact with a surface of the photoreceptor 1, and a voltage is applied,thereby being able to give a specified potential to the surface of thephotoreceptor 1. In embodiments, a contact charging member may be formedfrom a metal such as aluminum, iron or copper, a conductive polymermaterial such as a polyacetylene, a polypyrrole or a polythiophene, or adispersion of fine particles of carbon black, copper iodide, silveriodide, zinc sulfide, silicon carbide, a metal oxide or the like in anelastomer material such as polyurethane rubber, silicon rubber,epichlorohydrin rubber, ethylene-propylene rubber, acrylic rubber,fluororubber, styrene-butadiene rubber or butadiene rubber. Non-limitingexamples of metal oxides that may be used in embodiments include ZnO,SnO₂, TiO₂, In₂O₃, MoO₃ and complex oxides thereof. Further, aperchlorate may be added to the elastomer material to impartconductivity.

Further, a covering layer can also be provided on a surface of thecontact charging member of embodiments. Non-limiting examples ofmaterials that may be used in embodiments for forming a covering layerinclude N-alkoxy-methylated nylon, cellulose resins vinylpyridineresins, phenol resins, polyurethanes, polyvinyl butyrals, melamines andmixtures thereof. Furthermore, emulsion resin materials such as acrylicresin emulsions, polyester resin emulsions or polyurethanes, may beused. In order to further adjust resistivity, conductive agent particlesmay be dispersed in these resins, and in order to prevent deterioration,an antioxidant can also be added thereto. Further, in order to improvefilm forming properties in forming the covering layer, a leveling agentor a surfactant may be added to the emulsion resin in embodiments of theinvention.

The resistance of the contact charging member of embodiments may be from10 ⁰ to 10¹⁴ Ωcm, and from 10² to 10¹² Ωcm. When a voltage is applied tothis contact charging member, either a DC voltage or an AC voltage canbe used as the applied voltage. Further, a superimposed voltage of a DCvoltage and an AC voltage can also be used.

In the exemplary apparatus shown in FIG. 2, the contact charging memberof the contact charging device 2 is in the shape of a roller. However,such a contact charging member may be in the shape of a blade, a belt, abrush or the like.

Further, in embodiments an optical device that can perform desiredimagewise exposure to a surface of the electrophotographic photoreceptor1 with a light source such as a semiconductor laser, an LED (lightemitting diode) or a liquid crystal shutter, may used as the exposuredevice 3.

Furthermore, a known developing device using a normal or reversaldeveloping agent of a one-component system, a two-component system orthe like may be used in embodiments as the developing device 4. There isno particular limitation on toners that may be used in embodiments ofthe invention.

Contact type transfer charging devices using a belt, a roller, a film, arubber blade or the like, or a scorotron transfer charger or a corotrontransfer charger utilizing corona discharge may be employed as thetransfer device 5, in various embodiments.

Further, in embodiments, the cleaning device 7 may be a device forremoving a remaining toner adhered to the surface of theelectrophotographic photoreceptor 1 after a transfer step, and theelectrophotographic photoreceptor 1 repeatedly subjected to theabove-mentioned image formation process may be cleaned thereby. Inembodiments, the cleaning device 7 may be a cleaning blade, a cleaningbrush, a cleaning roll or the like. Materials for the cleaning bladeinclude urethane rubber, neoprene rubber and silicone rubber.

In the exemplary image forming device shown in FIG. 2, the respectivesteps of charging, exposure, development, transfer and cleaning areconducted in turn in the rotation step of the electrophotographicphotoreceptor 1, thereby repeatedly performing image formation. Theelectrophotographic photoreceptor 1 may be provided with specifiedsilicon compound-containing layers and photosensitive layers thatsatisfy equation (1), as described above, and thus photoreceptors havingexcellent discharge gas resistance, mechanical strength, scratchresistance, particle dispersibility, etc., may be provided. Accordingly,even in embodiments in which the photoreceptor is used together with thecontact charging device or the cleaning blade, or further with sphericaltoner obtained by chemical polymerization, good image quality can beobtained without the occurrence of image defects such as fogging. Thatis, embodiments of the invention provide image forming apparatuses thatcan stably provide good image quality for a long period of time isrealized.

FIG. 3 is a cross sectional view showing another exemplary embodiment ofan image forming apparatus. The image forming apparatus 220 shown inFIG. 3 is an image forming apparatus of an intermediate transfer system,and four electrophotographic photoreceptors 401 a to 401 d are arrangedin parallel with each other along an intermediate transfer belt 409 in ahousing 400.

Here, the electrophotographic photoreceptors 401 a to 401 d carried bythe image forming apparatus 220 are each the electrophotographicphotoreceptors of the invention. Each of the electrophotographicphotoreceptors 401 a to 401 d may rotate in a predetermined direction(counterclockwise on the sheet of FIG. 3), and charging rolls 402 a to402 d, developing device 404 a to 404 d, primary transfer rolls 410 a to410 d and cleaning blades 415 a to 415 d are each arranged along therotational direction thereof. In each of the developing device 404 a to404 d, four-color toners of yellow (Y), magenta (M), cyan (C) and black(B) contained in toner cartridges 405 a to 405 d can be supplied, andthe primary transfer rolls 410 a to 410 d are each brought into abuttingcontact with the electrophotographic photoreceptors 401 a to 401 dthrough an intermediate transfer belt 409.

Further, a laser light source (exposure unit) 403 is arranged at aspecified position in the housing 400, and it is possible to irradiatesurfaces of the electrophotographic photoreceptors 401 a to 401 d aftercharging with laser light emitted from the laser light source 403. Thisperforms the respective steps of charging, exposure, development,primary transfer and cleaning in turn in the rotation step of theelectrophotographic photoreceptors 401 a to 401 d, and toner images ofthe respective colors are transferred onto the intermediate transferbelt 409, one over the other.

The intermediate transfer belt 409 is supported with a driving roll 406,a backup roll 408 and a tension roll 407 at a specified tension, androtatable by the rotation of these rolls without the occurrence ofdeflection. Further, a secondary transfer roll 413 is arranged so thatit is brought into abutting contact with the backup roll 408 through theintermediate transfer belt 409. The intermediate transfer belt 409 whichhas passed between the backup roll 408 and the secondary transfer roll413 is cleaned up by a cleaning blade 416, and then repeatedly subjectedto the subsequent image formation process.

Further, a tray (tray for a medium to which a toner image is to betransferred) 411 is provided at a specified position in the housing 400.The medium to which the toner image is to be transferred (such as paper)in the tray 411 is conveyed in turn between the intermediate transferbelt 409 and the secondary transfer roll 413, and further between twofixing rolls 414 brought into abutting contact with each other, with aconveying roll 412, and then delivered out of the housing 400.

According to the exemplary image forming apparatus 220 shown in FIG. 3,the use of electrophotographic photoreceptors of embodiments of theinvention as electrophotographic photoreceptors 401 a to 401 d mayachieve discharge gas resistance, mechanical strength, scratchresistance, etc. on a sufficiently high level in the image formationprocess of each of the electrophotographic photoreceptors 401 a to 401d. Accordingly, even when the photoreceptors are used together with thecontact charging devices or the cleaning blades, or further with thespherical toner obtained by chemical polymerization, good image qualitycan be obtained without the occurrence of image defects such as fogging.Therefore, also according to the image forming apparatus for color imageformation using the intermediate transfer body, such as this embodiment,the image forming apparatus which can stably provide good image qualityfor a long period of time is realized.

The invention should not be construed as being limited to theabove-mentioned embodiments. For example, each apparatus shown in FIG. 2or 3 may be equipped with a process cartridge comprising theelectrophotographic photoreceptor 1 (or the electrophotographicphotoreceptors 401 a to 401 d) and charging device 2 (or the chargingdevices 402 a to 402 d). The use of such a process cartridge allowsmaintenance to be performed more simply and easily.

Further, in embodiments, when a charging device of the non-contactcharging system such as a corotron charger is used in place of thecontact charging device 2 (or the contact charging devices 402 a to 402d), sufficiently good image quality can be obtained.

Furthermore, in the embodiment of an apparatus that is shown in FIG. 2,a toner image formed on the surface of the electrophotographicphotoreceptor 1 is directly transferred to the medium P to which thetoner image is to be transferred. However, the image forming apparatusof the invention may be further provided with an intermediate transferbody. This makes it possible to transfer the toner image from theintermediate transfer body to the medium P to which the toner image isto be transferred, after the toner image on the surface of theelectrophotographic photoreceptor 1 has been transferred to theintermediate transfer body. As such an intermediate transfer body, therecan be used one having a structure in which an elastic layer containinga rubber, an elastomer, a resin or the like and at least one coveringlayer are laminated on a conductive support.

In addition, the image forming apparatus of embodiments may be furtherequipped with a static eliminator such as an erase light irradiationdevice. This may prevent incorporation of residual potential intosubsequent cycles when the electrophotographic photoreceptor is usedrepeatedly. Accordingly, image quality can be more improved.

EXAMPLES

The invention will be illustrated in greater detail with reference tothe following Examples and Comparative Examples, but the inventionshould not be construed as being limited thereto. In the followingexamples and comparative examples, all the “parts” are given by weightunless otherwise indicated.

Example 1 Preparation of Arylamine Intermediate

To a 2-liter 3-necked flask is fitted an argon inlet, mechanicalstirrer, and Dean-Stark trap. The flask is charged with 103.5 gbisformyl-N,N-diphenyl-4-aminobiphenyl dissolved in 400 mL toluene. Tothis, 114.4 g malonic acid and 93.6 g piperidine are added. After aninitial exotherm, has subsided, the reaction vessel is heated at refluxovernight. 200 mL toluene is distilled off, and then the reaction isdiluted with 250 mL THF (tetrahydrofuran), which is initiator free, and250 mL methanol. 3 g of palladium on charcoal (10%, wet) is added andthe reaction vessel is placed under an atmosphere of hydrogen (1-2atm.). The reaction is stirred at room temperature overnight, and thendiluted with 1 L ethylacetate and washed successively with 10 wt %sulfuric acid (3 times with 500 mL each time), 10 wt % Rochelle salt (1time at 500 mL), and saturated sodium chloride (I time at 500 mL). Theethylacetate is dried and removed. The residue is dissolved in methanol(200 mL), and 38.2 g potassium methoxide is added. The homogeneoussolution is stirred for 1 hour at room temperature. Next, 800 mLisopropanol is added and the mixture is distilled to remove 500 mLwithout recirculation. The mixture is cooled, and 500 mL heptane isadded to complete the precipitation. The solid is filtered and washedwith 500 mL heptane and dried under vacuum at 50° C. overnight. Theyield is 87.9 g N,N-[3-carboxypropyl phenyl]-4-aminobiphenyl dipotassiumsalt at an overall 60% yield.

Example 2 Preparation of Arylamine Intermediate

To a 2-liter 3-necked flask is fitted an argon inlet, mechanicalstirrer, and Dean-Stark trap. The flask is charged with 37 gbisformyl-N,N-diphenyl-4-aminobiphenyl dissolved in 165 mL toluene. Tothis, 40.9 g malonic acid and 33.5 g piperidine are added. After aninitial exotherm, has subsided, the reaction vessel is heated at refluxovernight. 90 mL toluene is distilled off, and then the reaction isdiluted with 90 mL THF (tetrahydrofuran), which is initiator free, and90 mL methanol. 1.1 g of palladium on charcoal (10%, wet) is added andthe reaction vessel is placed under an atmosphere of hydrogen (1-2atm.). The reaction is stirred at room temperature overnight, and thendiluted with 360 mL ethylacetate and washed successively with 10 wt %sulfuric acid (3 times with 165 mL each time), 10 wt % Rochelle salt (1time at 165 mL), and saturated sodium chloride (I time at 165 mL). Theethylacetate is collected and 11.5 g clay is added and the mixtureheated to a boil and then filtered while hot. The filtrate is collected,dried, and removed. The residue is dissolved in methanol (70 mL), and13.6 g potassium methoxide is added. The homogeneous solution is stirredfor 1 hour at room temperature. Next, 290 mL isopropanol is added. Theflask is fitted with a fractionating column and the mixture is distilledto remove 100 mL without recirculation at a boiling point between 72 and75° C. An additional 100 mL isopropanol is added, and 100 mL is removedwithout recirculation until a boiling point of 82° C. is achieved. Themixture is cooled, and 180 mL heptane is added to complete theprecipitation. The solid is filtered and washed with 180 mL heptane. Thesolid is dissolved in 70 ml methanol and 0.270 g (2 mol %) potassiummethoxide is added. The homogeneous solution is stirred for 1 hour atroom temperature. Next, 290 mL isopropanol is added. The flask is fittedwith a fractionating column and the mixture is distilled to remove 100mL without recirculation at a boiling point between 72 and 75° C. Anadditional 100 mL isopropanol is added, and 100 mL is removed withoutrecirculation until a boiling point of 82° C. is achieved. The mixtureis cooled, and 180 mL heptane is added to complete the precipitation.The solid is filtered and washed with 180 mL heptane and dried undervacuum at 50° C. overnight. The yield is 35.2 g N,N-[3-carboxypropylphenyl]-4-aminobiphenyl dipotassium salt at an overall 66% yield.

Example 3 Preparation of Arylamine Charge Transport Molecule

In a suitable reaction apparatus, the material from Example 1 (116 g) isdissolved in a mixture of DMF (200 mL), isopropyl alcohol (IPA, 100 mL)and 3-iodopropylmethyldiisopropoxysilane (111 g) is added and themixture heated at 90° C. under an atmosphere of nitrogen for 5 hoursafter which the mixture is cooled to room temperature. Toluene (500 mL)is added and the solution is washed with water and saturated sodiumchloride solution. On removal of the volatile organic solvents andchromatographing on silica gel, the compound (33) can be obtained insuitable purity for application in the preparation of siloxanecontaining charge transporting layers for electrophotographicapplication.

Example 4 Preparation of Photoreceptor Layer

11 parts of compound (33), 5.8 parts of compound III-3, 0.2 parts of1-(dimethoxymethylsilyl)-1H,2H,2H-perfluorononane, 1 part ofhexamethylcyclotrisilane and 11 parts of methanol were mixed, and 2parts of an ion exchange resin (AMBERLIST H15) was added thereto,followed by stirring for 2 hours. Furthermore, 32 parts of butanol and4.92 parts of distilled water were added to this mixture, followed bystirring at room temperature for 30 minutes. Then, the resulting mixturewas filtered to remove the ion exchange resin, and 0.180 parts ofaluminum trisacetylacetonate (Al(AcAc)₃), 0.180 parts of acetylacetone(AcAc), 2 parts of a polyvinyl butyral resin (trade name: S-LEC KW-1,manufactured by Sekisui Chemical Co., Ltd.), 0.0180 parts ofbutylated-hydroxytoluene (BHT) and 0.261 parts of a hindered phenolantioxidant (IRGANOX 1010) were added to a filtrate obtained, andthoroughly dissolved therein for 2 hours to obtain a coating solutionfor a protective layer. This coating solution was applied onto theabove-mentioned charge transfer layer by dip coating (coating speed:about 170 mm/min), and dried by heating at 130° C. for one hour to formthe protective layer having a film thickness of 3 μm, thereby obtaininga desired electrophotographic photoreceptor.

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

1. A process for forming a 4-aminobiphenyl derivative arylaminecompound, comprising: (i) providing a first disubstituted4-aminobiphenyl compound; (ii) optionally formylating said firstdisubstituted 4-aminobiphenyl compound to form a bisformyl substitutedcompound, where said first disubstituted 4-aminobiphenyl compound is nota bisformyl substituted compound; (iii) acidifying said bisformylsubstituted compound to convert formyl functional groups into acidfunctional groups to form an acidified compound; and (iv) hydrogenatingsaid acidified compound to saturate at least one unsaturated doublebonds in the acidified compound, wherein there is provided a seconddisubstituted 4-aminobiphenyl compound.
 2. The process according toclaim 1, wherein said first disubstituted 4-aminobiphenyl compound isrepresented by the following general formula:4-aminobiphenyl-(R¹)(R²) where R¹ and R², which can be the same ordifferent, represent aromatic or heterocyclic groups.
 3. The processaccording to claim 2, wherein R¹ and R² are the same.
 4. The processaccording to claim 2, wherein R¹ and R² are different.
 5. The processaccording to claim 2, wherein R¹ and R² are aromatic groups selectedfrom the group consisting of substituted or unsubstituted phenyl groups,substituted or unsubstituted groups including two or more phenyl groups,substituted or unsubstituted fused polycyclic hydrocarbons, and mixturesthereof.
 6. The process according to claim 2, wherein R¹ and R² areheterocyclic groups selected from the group consisting of substituted orunsubstituted 3- to 10-membered rings containing one or moreheteroatoms.
 7. The process according to claim 1, wherein saidformylating is conducted by way of a Vilsmeier reaction.
 8. The processaccording to claim 1, wherein said formylating is conducted by treatinga halogenated derivative of the first disubstituted 4-aminobiphenylcompound with n-butyllithium followed by dimethytlformamide.
 9. Theprocess according to claim 1, wherein said formylating is conducted bytreating a halogenated derivative of the first disubstituted4-aminobiphenyl compound with hexamethylene tetraamine in the presenceof trifluoroacetic acid.
 10. The process according to claim 1, whereinsaid first disubstituted 4-aminobiphenyl compound is a bisformylsubstituted compound represented by the following general formula:4-aminobiphenyl-(R¹)(R²) where R¹ and R², which can be the same ordifferent, represent aromatic or heterocyclic groups.
 11. The processaccording to claim 2, wherein said bisformyl substituted compound isrepresented by the following general formula:4-aminobiphenyl-(R¹—CH═O)(R²—CH═O).
 12. The process according to claim1, wherein said acidifying comprises a condensation reaction.
 13. Theprocess according to claim 1, wherein said acidifying is conducted byway of a Knoevenagel condensation reaction.
 14. The process according toclaim 1, wherein said acidifying is conducted by way of a Doebnermodification condensation reaction.
 15. The process according to claim1, wherein said acidifying converts —CH═O formyl functional end groupsinto —C═C—COOH carboxylic acid functional end groups.
 16. The processaccording to claim 2, wherein said acidified compound is represented bythe following general formula:4-aminobiphenyl-(R¹—C—C—COOH)(R²—C═C—COOH).
 17. The process according toclaim 1, wherein said acidified compound is used directly in the step(iii) without purification or isolation.
 18. The process according toclaim 1, wherein said hydrogenating is conducted in the presence of acatalyst.
 19. The process according to claim 8, wherein said catalyst issupported on a carbon substrate.
 20. The process according to claim 1,wherein said second disubstituted 4-aminobiphenyl compounds is acarboxylic acid compound.
 21. The process according to claim 1, furthercomprising forming an alkali metal salt of the second disubstituted4-aminobiphenyl compound.
 22. The process according to claim 2, whereinsaid second disubstituted 4-aminobiphenyl compound is represented by thefollowing general formula:4-aminobiphenyl-(R¹—CH₂—CH₂—COO⁻X₁ ⁺)(R²—CH₂—CH₂—COO⁻X₂ ⁺) wherein X₁and X₂, which can be the same or different, are cationic groups.
 23. Theprocess according to claim 22, wherein said cationic groups are alkalimetals.